Question

From the following, identify the set that contains all meta directing groups:

• A. \(-\text{NHCOCH}_3\), \(-\text{Cl}\), \(-\text{CHO}\)
• B. \(-\text{OCH}_3\), \(-\text{NO}_2\), \(-\text{NH}_2\)
• C. \(-\text{CN}\), \(-\text{COCH}_3\), \(-\text{COOCH}_3\)
• D. \(-\text{OH}\), \(-\text{CN}\), \(-\text{CH}_3\)

Hint:

When evaluating directing effects in aromatic substitution, it's crucial to consider the electronic effects of substituents: electron-donating groups typically direct ortho/para, while electron-withdrawing groups typically direct meta.

Answer 1

The Correct Option is C

In aromatic chemistry, meta-directing groups are typically deactivating and electron-withdrawing. The electron-withdrawing nature of these groups through inductive or resonance effects makes them meta-directors. We examine each set:  

Option 1: \(-\text{NHCOCH}_3\) (amide) is a meta director.
\(-\text{Cl}\) (chloro) is an ortho/para director.
\(-\text{CHO}\) (formyl) is a meta director.
This set contains both meta and ortho/para directors.

 Option 2: \(-\text{OCH}_3\) (methoxy) is an ortho/para director.
\(-\text{NO}_2\) (nitro) is a strong meta director.
\(-\text{NH}_2\) (amino) is an ortho/para director.
This set also contains both meta and ortho/para directors. 

Option 3: \(-\text{CN}\) (cyano) is a strong meta director.
\(-\text{COCH}_3\) (acetate) is a meta director.
\(-\text{COOCH}_3\) (ester) is a meta director.
All groups in this set are meta directors, making this the correct choice. 

Option 4: \(-\text{OH}\) (hydroxyl) is an ortho/para director.
\(-\text{CN}\) (cyano) is a meta director.
\(-\text{CH}_3\) (methyl) is an ortho/para director.
This set contains both meta and ortho/para directors.